Code a folder-sorting system for messages

We have an iPhone application that is about to launch where users can send us messages and we respond. ? The messages come to a server where they are put in a "message" folder. We need the ability to add different folders for the people answering the messages where the messages will sort as they come in. ? (for example, we may have three people answering messages. ? The first message will go in the first folder, the second goes in the second person's folder and the third goes in the the third persons folder. ? The fourth would then go in the first person's and so on.)? We need the ability to add/take away user folders as well.